1. Field of the Invention
The present invention relates to an exhaust-heat recovery system for an engine in order to utilize exhaust heat for air conditioning, heating, etc. by means of efficient recovery thereof from the engine.
2. Description of the Related Art
There has been conventionally well known a system disclosed in JP 1-132415A, which utilizes exhaust heat from an engine for heating the interior of a vehicle. The system heats a coolant for the engine utilizing the exhaust heat and sends a heating wind into the interior of the vehicle by passing the heated coolant through a heat exchanger disposed along a warm-air duct.
The system has a problem that the volume and temperature of the exhaust vary depending upon the magnitude of a load on the engine. When the load on the engine is large enough to generate sufficient exhaust heat, a coolant for the engine is efficiently heated using the exhaust heat. When the engine is idling (the vehicle is at rest but the engine is still in operation) in a cold period such as winter, the volume of the exhaust is small and the temperature thereof is also low due to a very small load.
Therefore, when the engine is idling in a cold period, it is difficult to heat the coolant for the engine using only the exhaust from the engine in order to heat the interior of the vehicle.